Spark-plug



H. M. CROWTHER.

SPARK PLUG. I APPLICATION FILED AUG.28| I919. 1,356,129, Patented Oct. 19, 1920.

FIG. I.

INSU T/DN I N VEN TOR. Henry/ Cnawruzn UNITED STATES PATENT OFFICE.

HENRY M. CROWTHER, OF KINGMAN, ABLTZGNA.

SPARK-PLUG.

Specification of Letters Patent.

PatentedOct. 19,1920.

Application filed August 28, 1919. Serial No. 320,533.

T 0 all whom it may concern:

Be it known that I, HENRY M. Cnow'rrinn,

a citizen of the United States, residing at Kingman, in the county of Mohave and State of Arizona, have invented new and useful Improvements in Spark-Plugs, of which the following is a specification.

My object is to make a self-cleaning spark plug and my invention consists of the detail on the line 22 of Fig. 1.

Fig. 3 is a bottom plan view looking in the direction indicated by the arrow 3 in Fig. 2.

The insulating core 1 is preferably formed of porcelain, mica or other strong, hard, refractory, non-conducting material, and comprises an upper conical portion 5, a central cylindrical portion 3, an annular retaining flange 4:, a lower conical portion 5, and a lower cylindrical portion 6, there being a central bore 7 extending from the upper end face 8 to the lower end face 9. A conductor feed rod 10 is inserted upwardly through the bore 7 and has a stop flange 11 near its lower end, recessed into the lower end face 9 to limit the upward I movement of the rod. A cap 12 fits upon the upper end of the insulator against the upper face 8 and the rod 10 extends through the cap. A binding post nut 13 fits upon the rod against the cap 12 and a second binding post nut 14 is screwed upon the rod against'the nut 13.

The metal casing 15 has a hexagonal upper end 16 forming a wrench seat and it has an internal screw thread17. A cushion 18 of asbestostpaper or other suitable material is placed against the lower face of the lower conical portion 5 and the insulator is inserted downwardly into the casing 15 against a shoulder 19. A cushion 20 is placed against the upper face of the flange 4:. and the externally screw threaded bushing 21 is placed around the cylindrical portion 3 and is screwed into the casing 15 against the cushion 20.

' The cylindrical portion 6 of the insulator is considerably reduced in size relative to the cylindrical portion 3. The externally threaded nipple 22 extends. downwardly from the shoulder 19 of the casing 15 to a point considerably below the lower end 9 of the insulator, thus makin a chamber 23 around the cylindrical port1on 6. The lower end of the conductor rod 10 extends below the lower end of the nipple 22 and serves as one terminal 24 for the spark. The terminal 25 extends from the lower end of the nipple 22, there being a spark gap 26 between the terminal 24 and 25.

A circular boss 28 extends upwardly from the plate 27, thereby forming an annular angular seat 29. A coil 30 of wireis made slightly shorter than the cylindrical portion 6 of the insulator and the lower end. of the coil fits tightly in the seat 29. The coil 30 is slightly larger than the cylindrical portion 6 of the insulator and is held clear and out of contact with "ihe insulator. A coil -31 fits tightly upon the lower end of the rod 10 against the plate 27 so as to hold the plate and coil in place and so that the coil. 31 may be forcibly removed from the rod 10 and then the plate 27 and the coil 30 may be easily removed.

The trouble with the ordinary spark plugs is that the insulator cores will become coated with smoke, lamp black or carbon from poor combustion and from the splashing of the cylinder oil and this coat forms more or less of an electric conductor to carry the electricity from the central feed rod along the surface of the insulator core to the metallic casing. In this typeof spark plug a metallic casing forms one side of the spark gap. In order that a spark plug shall be satisfactory it is necessary that the entire force of the electric impulse shall pass through the spark gap and any leakage of the current due to the depositing of carbon upon the insulator core will reduce the necessary that a 'full short circuit be established between the feed rod and the methe spark and any eifective gap or leak in (2 mph .will burn and in burning will consume the lamp black deposited upon the insulator and will produce a heat sulficient to prevent the condensation of the exhaust gas, thereby preventing the deposit of lamp black upon the insulator. Furthermore, the coil 30 will 1'02211 a shield to protect the insulator from the cylinder: The oil which may splash upon the coil will be efi'ectually burned away and this will serve to keep the insulator clean In order to prevent the short circuiting or leaking oi: the electric current it is only necessary that a small part of the belt v around the insulator be maintained hot enough to burn away the lamp black or prevent its deposit. The coil 31 is intended to simply be a retainer and to hold the heater in place.

Various changes may be made without departing from the spiritof my invention as claimed.

I claim: y

1. Aself cleaning spark plug comprising in combination with a casing carrying a main insulator having a reduced inner end and a conductor rod mounted through the insulator, a wire coil disposed about the reduced inner end of the insulator and spaced therefrom and spaced from the inner wall of the casing, and a washer for holding the coil'in place.

2.'In a self'cleaning spark plug a wire coil disposed about the lower end of the insulator and spaced therefrom, so as to protect the insulator from oil and so as to make a heater to burn the lamp black.

In testimony whereof I have signed my name to this sfiecification.

ENRY M. CROWTHER. 

